JPH026014A - Manufacture of composite pipe - Google Patents

Abstract

PURPOSE:To obtain a composite pipe uniform in pressure resisting property over its full length by inserting a pipe which is made of a synthetic resin and has an outside diameter smaller than the inside diameter of a metallic pipe and reducing the diameter of the metallic pipe by cold drawing. CONSTITUTION:A pipe 1 which is made of a synthetic resin and has an outside diameter smaller than the inside diameter of a seamless metallic pipe 2 manufactured by extrusion molding, etc., is inserted into the metallic pipe 2. After insertion, cold drawing is performed on the pipes by passing the pipes through a die 3 so as to reduce the diameter of the pipe 2 and cause the metallic pipe 2 to closely adhere to the outer periphery of the pipe 1. Then a coating layer 4 of a synthetic resin is formed on the outer peripheral surface of the metallic pipe 2 by using an extrusion molding machine 6. As a result, a composite pipe which as a uniform pressure resisting property and is improved in dimensional accuracy and strength is manufactured. Thus the quality of the composite pipe is maintained at a high level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a composite pipe in which the outer periphery of a synthetic resin pipe is covered with a metal pipe over almost its entire length.

[Conventional technology]

Conventional composite pipes are made by wrapping a band-shaped metal sheet around the outer periphery of a synthetic resin pipe and making it tightly adhered, and then welding the edges of the metal sheets that come together as they are wrapped to form a metal pipe. Alternatively, there is a method in which a synthetic resin tube is continuously extruded inside the metal tube immediately after welding and forming the metal tube in the same manner as above, but in both cases, welding is essential for forming the metal tube. Ta.

[Problem to be solved by the invention]

However, if there is a defect in the welding, the pressure resistance of the metal tube may not be uniform over its entire length, and the predetermined pressure resistance may become unstable in some parts. In addition, if the excess height of the welded part becomes too large, the thickness of the coating layer will not be uniform in the circumferential direction when extruding a coating layer around the outer periphery of a metal tube, and furthermore, the excess height of the welded part If the height of the metal pipe is uneven in the longitudinal direction, the thickness of the coating layer tends to be uneven in the longitudinal direction of the pipe, which may require a lot of effort in selecting and managing welding conditions. there were.

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to easily manufacture a composite pipe with uniform pressure resistance over its entire length.

[Means to solve the problem]

The characteristic structure of the method for manufacturing a composite pipe according to the present invention is that a synthetic resin pipe whose outer diameter is smaller than the inner diameter of the metal pipe is inserted inside a metal pipe, and then the diameter of the metal pipe is reduced by cold drawing. The purpose is to adhere closely to the outer periphery of the synthetic resin pipe.
Its actions and effects are as follows.

[For production]

In other words, the work of inserting a metal tube into a synthetic resin tube can be done smoothly because the outer diameter of the synthetic resin tube is smaller than the inner diameter of the metal tube, and the metal tube has uniform pressure-resistant joints along its entire length. It is possible to use a ready-made extrusion molded product, and after the above-mentioned insertion process, the metal tube is reduced in diameter by cold drawing and tightly attached to the outer periphery of the synthetic resin tube, making it possible to create an integrated composite tube. Can be formed.

〔Effect of the invention〕

Therefore, a composite tube with uniform pressure resistance over its entire length can be manufactured by simple manufacturing management, and dimensional accuracy and strength are improved, making it easier to maintain high quality as a composite tube.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

The synthetic resin pipe (1) has corrosion resistance against transport fluids, is lightweight, and has heat retention properties, the metal pipe (2) has pressure resistance, and ease of piping construction that requires bending. With advantages, for gas pipes, hot water supply, water supply,
When manufacturing composite pipes for hot water heating, etc., as shown in Figure 1, a seamless metal pipe (2) made by extrusion molding etc. is lined with a metal tube (2) whose outer diameter is larger than the inner diameter of the metal pipe (2). A small synthetic resin pipe (1) is inserted, and then, as shown in Fig. 2, the diameter of the metal pipe (2) is reduced by cold drawing to draw the pipe into a bow through a die (3). ), and finally, as shown in Figure 3, attach the metal tube (
An extrusion molding machine (
6).

Next, an example of manufacturing the composite pipe will be described.

Purity 99.7% or more (7) 7 Lumi=UL, (J
IS) I-4080 alloy number 1.070), 400
A metal tube (2) with an inner diameter of 20 mm, an outer diameter of 21 mm, and a total length of 40 m was formed by extrusion molding at ℃, and a synthetic resin tube (1) with an inner diameter of 14 mm, an outer diameter of 17 mm, and a total length of 100 m was extruded from cross-linked polyethylene. , metal tube (
2) After inserting the synthetic resin pipe (1) into the die (3)
The inside diameter of the synthetic resin tube (1) is 12.7 mm, and then a coating layer with a thickness of 0.5 mm is formed on the outer periphery of the metal tube (2) by extrusion molding of polyethylene.

[Another example]

The metal tube (2) may be made of copper or iron in addition to aluminum.

The synthetic resin pipe (1) may be made of non-crosslinked polyethylene or other resin materials in addition to crosslinked polyethylene, and especially when crosslinked polyethylene is used,
It has excellent heat resistance and is suitable for hot water supply pipes.

The coating layer (4) is not particularly necessary, but if it is present, corrosion of the outer circumferential surface of the metal tube (2) can be prevented.

In order to improve the flexibility of the composite tube, the metal tube (2) is passed through a pair of rollers (5) shown in FIGS. 5 and 6 after cold drawing to form a corrugated tube. The cross-sectional shape shown in FIG. 4 may be formed with unevenness in the direction.

The aluminum metal tube (2) preferably has a thickness of 0.2 aun or more from the viewpoint of workability and pressure resistance.

Note that although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structures and methods shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawings show an embodiment of the method for manufacturing a composite pipe according to the present invention.
Figures 3 to 3 are explanatory diagrams showing the manufacturing order, and Figure 1 is a perspective view.
2 and 3 are longitudinal sectional views, respectively, FIG. 4 is a longitudinal sectional view of a composite pipe according to another embodiment, FIG. 5 is a side view of a roller used in implementing another embodiment, and FIG. 5 is a sectional view taken along the line VI-VI in FIG. 5; FIG. (1)...Synthetic resin pipe, (2)...Metal pipe.

Claims (1)

[Claims] A method for manufacturing a composite pipe in which the outer periphery of a synthetic resin pipe (1) is covered almost over its entire length with a metal pipe (2), the outer diameter of which is the inner diameter of the metal pipe (2). A method for manufacturing a composite pipe, in which the smaller synthetic resin pipe (1) is inserted, and then the metal pipe (2) is reduced in diameter by cold drawing and brought into close contact with the outer periphery of the synthetic resin pipe (1).